This invention relates to an oscillator comprising a first and a second transistor each including a first main electrode, which first main electrodes are mutually coupled via a capacitor, and each including a second main electrode coupled to a gate electrode of the other transistor. The second main electrode of the first transistor is coupled to a first load circuit and the second main electrode of the second transistor is coupled to a second load circuit.
An oscillator of this type is generally known. If each load circuit is constituted by a resistor R and each first main electrode is connected to a current source that produces a current of the magnitude I, the oscillator will generate a square-wave output voltage between the two second main electrodes with a frequency f.sub.osc =I/(2C* V.sub.c), where C represents the capacitance value of the capacitor and V.sub.c is the voltage across this capacitor. The desired frequency f.sub.osc is obtained by selecting an appropriate value for the current I.
Because the conductance of a transistor is proportional to the square root of the main current through this transistor and because the conductance of a resistor R is constant (=1/R), the voltage V.sub.c (non-linear) becomes dependent on the current I. Consequently, the relation between the frequency f.sub.osc and the current I exhibits a non-linear characteristic. This is undesired, for example, in phase-locked loop applications in which an oscillator of this type is used.